1. Field of the Invention
The present invention relates to a keypad scanner mechanism and process and, more particularly, to such a keypad scanner mechanism and process for use in a cordless telephone.
2. Description of Related Art
A keypad is a common device for communicating with a microcontroller or other electronic circuitry and devices. In a microcontroller application, the software controlling the microcontroller identifies pressed keys of the keypad as a signal to the microcontroller to perform certain functions. A keypad consisting of an array of keys is essentially a collection of switches, each key forming a switch. Each switch (i.e., key) may be connected independently to an input port of a device, for example, a microcontroller, to which the keypad serves as an input. The interfacing and programming necessary to allow input to the device via the keypad is similar to the interfacing and programming necessary for accomplishing similar results with any other collection of switches.
Generally, the software for interpreting signals from a keypad must perform the tasks listed below:
1. Determine if any keys have been pressed; PA1 2. If a key has been pressed, determine which one; and PA1 3. Decide on an action, for example, data entry, based on the key that was pressed.
The software must perform these tasks in response to a number of activities on the keypad.
An integral element which detects the particular activities on a keypad and allows the activities to be acted upon by the device to which the keypad provides input is a keypad scanner mechanism. The keypad scanner mechanism is the device and process by which the rows and columns of a matrix keypad are examined to determine whether keys have been press ed and, if so, which keys.
When a key on a keypad is pressed, the keypad scanner mechanism detects a number of things that happen. First, the keypad scanner mechanism detects that a key has transmissioned from its open state to its closed state. When pressed, the key will physically bounce (i.e. , it will open and close randomly) before it stabilizes in a closed position. The key will be in its depressed state for some period of time, relatively long compared to the time period of the bounce. The keypad scanner mechanism must discern depressions of the key and distinguish from bounce. Further, it is often important that the keypad scanner mechanism detect how long a key is depressed, for example, a volume control which continues to adjust by either increasing or decreasing volume as the key is held down. When the key is released, the keypad scanner mechanism must detect that the key has been released and report that information to the user. Once so released, the key will bounce again and then go to a stable state of being released, and the keypad scanner mechanism must read such activities.
Prior to the present invention, a variety of keypad reporting systems have been in use. These keypad reporting systems have exhibited certain requirements and characteristics which are restricting or limiting in certain applications, for example, for cordless telephones. The requirements and characteristics include high cost of hardware to perform the reporting function and utilization through software of significant amounts of available processing power due to the necessity that functions be performed with a single processor. It would, therefore, be an improvement in the technology if a keypad reporting system were developed which employed more simplified and thus more cost-effective hardware and which allowed for the use of real time software which utilizes a minimum amount of the available processing power thereby allowing use of a smaller, less costly microcontroller that can run at a much lower clock speed thereby limiting power consumption. The keypad scanner mechanism of the present invention provides these improvements.
One particular application for which the keypad scanner mechanism of the present invention is well-suited is a cordless telephone. Cordless telephones may be contrasted with standard telephones in several respects. The standard telephone consists of a base unit and a handset unit connected to each other by an electrical cord. The base unit itself is connected by another cord to a receptacle on a wall, telephone pole or a similar immovable structure to which the telephone network line extends. Because of this connection to an immovable structure, the range of movement of the operator of the telephone is quite limited. Even when the cords connecting the handset unit to the base unit and the base unit to the wall are long, it can be cumbersome either to move the entire telephone around to make calls from different locations or to walk around with the handset unit once a call has been placed. The simple fact that there is always a continuous physical connection between the person making the phone call and the immovable wall or other fixed structure can be a great inconvenience.
The cordless telephone, on the other hand, represents a significant improvement over the standard telephone. In the conventional cordless telephone, the base unit is still connected to the receptacle on the immovable wall or the like by a cord so that message signals from the telephone network line may be received and transmitted. However, the handset unit of the cordless telephone is an independently operative unit from which calls may be made and by which calls may be received with no physical connection to the base unit. The handset unit has a transmitting/receiving system or transceiver, a loudspeaker in an earpiece and a microphone in a mouthpiece. The base unit and the handset unit of the cordless telephone communicate with each other over a communication channel established by the transmission and reception of electromagnetic waves, conventionally radio waves. The handset unit may then be taken considerable distances from the base unit while still making and receiving telephone calls. Since there is no telephone cord extending between the handset unit and the base unit, the operator is free to move about without hindrance.
Heretofore, keypad reporting systems have been developed and used, for example, in cordless telephones, to perform various functions. As previously described, however, there are a number of aspects of such keypad reporting systems that can be improved. The present keypad scanner mechanism provides these improved aspects.
Based upon the foregoing, those skilled in the art should now perceive that the keypad scanner mechanism of the present invention, for example, for use in cordless telephones, is an improvement over the existing technology. It is a shortcoming and deficiency of the prior art that such an improvement has not previously been conceived.